The Effect of Propeller Pitch on Ship Propulsion

The appropriate choice of a marine engine identified by using self-propulsion model tests is compulsory, in particular with respect to the improvement of vessel performances. Numerical simulations or experimental methods provide insight into the problem of flow, where fixed pitch propellers or controllable pitch propellers are preferred. While calculation methods are time consuming and computationally demanding for both propeller types, hydrodynamic performance assessment has more workload in controllable pitch propellers. This paper aims to describe and demonstrate the practicability and effectiveness of the self-propulsion estimation (SPE) method in understanding the effect of propeller pitch on ship propulsion. Technically, the hydrostatic and geometric characteristics of the vessel and open-water propeller performances are the focal aspects that affect the self-propulsion parameters estimated by the SPE method. The input coefficients for SPE have been identified using a code that generates propeller open-water performance curves. The propellers utilized to study pitch variations have been based on the Wageningen B-series propeller database. The method was first validated on the full size Seiun Maru ship whose sea trial tests are available in literature. After extensive calculations for full size KCS and DTC at service speeds, the study focused on the effect of the Froude number on propulsion parameters. These calculations have demonstrated that greater propeller pitch does not improve propulsion efficiency, and that maximum propeller efficiency changes with a ship\u27s forward speed

A study of semi-insulating GaN grown on AlN buffer/sapphire substrate by metalorganic chemical vapor deposition

We report the remarkably improved crystal quality of semi-insulating GaN grown by metalorganic chemical vapor deposition on an AlN buffer layer, which is deposited on sapphire substrate. The electrical and structural properties are characterized by dark current-voltage transmission line model and X-ray diffraction measurements. It is found that the crystal quality of the GaN epilayer is strongly related with the growth temperature of the decreased-temperature GaN interlayer. In comparison with the normal GaN grown on sapphire, the crystal quality is remarkably improved along with a semi-insulating electrical character. The high-mobility field effect transistors device based on the semi-insulating GaN shows good pinch off properties. Our electrical measurement results of GaN grown directly on an AlN buffer indicated that the as-grown-undoped GaN is naturally semi-insulating material. The origination of the residual donors in normal GaN grown on sapphire substrate is also discussed. © 2006 Elsevier B.V. All rights reserved

Assessment of the relationship between a narrow fragmented QRS complex and coronary slow flow

Background: The coronary slow flow (CSF) phenomenon is a delayed antegrade progression of contrast agent to the distal branch of a coronary artery in the absence of obstructive coronary artery disease (CAD). A narrow fragmented QRS (fQRS) has been reported as a significant predictor of sudden cardiac death in patients with idiopathic dilated cardiomyopathy. The present study aimed to investigate the relationship between a narrow fQRS on the admission electrocardiogram (ECG) and CSF on coronary angiography. Methods: This study included 165 consecutive patients (112 CSF, 53 controls) who underwent first-time diagnostic conventional coronary angiography for suspected CAD. Coronary flow was quantified by thrombolysis in myocardial infarction (TIMI) frame count (TFC). The patients were divided into two groups according to the presence or absence of a narrow fQRS complex on the admission ECG. Results: Forty four patients were in the fQRS group (mean age, 52.97 ± 3.13 years). There was no difference between the two groups with respect to age, gender, body mass index, family history, hyperlipidemia, hypertension, or diabetes mellitus. The extent of CSF was significantly greater in the fQRS group compared to the non-fragmented group (p < 0.001). A significant correlation was also found between mean TFC values and fQRS (p < 0.001). On multivariate analysis, only CSF (p = 0.03) was a significant independent predictor for narrow fQRS, after adjustment for other parameters. Conclusions: The narrow fQRS is a simple, inexpensive, and readily available noninvasive ECG parameter that may be a new potential indicator of myocardial damage in patients with CSF.

The diagnostic value of serum copeptin levels in an acute pulmonary embolism

Background: Acute pulmonary embolism (APE) is a common disease which is associated with high mortality and morbidity. Circulating level of copeptin, which was demonstrated to be elevated in heart failure, acute myocardial infarction and pulmonary arterial hypertension, were reported to be independent predictors of poor outcome in recent studies. The aim of the present study was to investigate the clinical utility of copeptin in the diagnosis of APE. Methods: A total of 90 consecutive patients, admitted to emergency service due to acute chest pain and/or dyspnea and who underwent pulmonary computerized tomography angiography (CTA) due to suspicion of APE, were included in this prospective study. The patients diagnosed with APE were defined as APE (+) group and the remaining individuals with normal pulmonary CTA result were defined as APE (–) group. Results: Copeptin levels (7.76 ± 4.4 vs. 3.81 ± 1.34 ng/dL; p < 0.001) were higher in the APE (+) group as compared to the APE (–) group. Copeptin was significantly positively correlated with B-type natriuretic peptide (r = 0.434, p < 0.001), D-dimer (r = 0.315, p = 0.003) and troponin I (r = 0.300, p = 0.004) and inversely correlated with arterial oxygen saturations (r = –0.533, p < 0001). When the correlation of copeptin with right ventricular dysfunction parameters was investigated, it was significantly inversely correlated with the tricuspid annular plane systolic excursion (r = –0.521, p < 0.001) and positively correlated with right to left ventricle ratio (r = 0.329, p = 0.024). Copeptin (OR 1.836, 95% CI 1.171–2.878, p = 0.008) was found as a significant independent predictor of APE in a multivariate analysis, after adjusting for other risk parameters.  Conclusions: Copeptin is a promising new biomarker, which may be used to support the need for further investigations and to improve the diagnosis of patients with APE.

Ozone Therapy and Hyperbaric Oxygen Treatment in Lung Injury in Septic Rats

Various therapeutic protocols were used for the management of sepsis including hyperbaric oxygen (HBO) therapy. It has been shown that ozone therapy (OT) reduced inflammation in several entities and exhibits some similarity with HBO in regard to mechanisms of action. We designed a study to evaluate the efficacy of OT in an experimental rat model of sepsis to compare with HBO. Male Wistar rats were divided into sham, sepsis+cefepime, sepsis+cefepime+HBO, and sepsis+cefepime+OT groups. Sepsis was induced by an intraperitoneal injection of Escherichia coli; HBO was administered twice daily; OT was set as intraperitoneal injections once a day. The treatments were continued for 5 days after the induction of sepsis. At the end of experiment, the lung tissues and blood samples were harvested for biochemical and histological analysis. Myeloperoxidase activities and oxidative stress parameters, and serum proinflammatory cytokine levels, IL-1β and TNF-α, were found to be ameliorated by the adjuvant use of HBO and OT in the lung tissue when compared with the antibiotherapy only group. Histologic evaluation of the lung tissue samples confirmed the biochemical outcome. Our data presented that both HBO and OT reduced inflammation and injury in the septic rats' lungs; a greater benefit was obtained for OT. The current study demonstrated that the administration of OT as well as HBO as adjuvant therapy may support antibiotherapy in protecting the lung against septic injury. HBO and OT reduced tissue oxidative stress, regulated the systemic inflammatory response, and abated cellular infiltration to the lung demonstrated by findings of MPO activity and histopathologic examination. These findings indicated that OT tended to be more effective than HBO, in particular regarding serum IL-1β, lung GSH-Px and histologic outcome